Delayed gelling of sodium silicate and use therefor



,[Hh-DU United States Patent 3,435,899 DELAYED GELLING 0F SODIUMSILICATE AND USE THEREFOR Homer C. McLaughlin and Joseph Ramos, Duncan,0kla., assignors to Halliburton Company, Duncan, Oklm, a corporation ofDelaware No Drawing. Filed Apr. 24, 1967, Ser. No. 632,929 Int. Cl. E2lb33/13 US. Cl. 166-292 22 Claims ABSTRACT OF THE DISCLOSURE A liquidsealing composition having a delayed gel time is formed by adding to asodium 7 (I plexed polyxalentfiilil. Slow release of the polyvalentiii''ta'l ion from the complex results in a delayed setting or gellingof the sodium silicate solution. Release of the polyvalent metal ion maybe achieved by use of a material which will destroy the complex so thatpolyvalent metal ion is liberated at the desired time. Release of thepolyvalent ion may also slowly occur from some cornplexes without thenecessity of adding a complex destroyer.

Background of the invention This invention relates to a new and improvedmethod and composition for plugging or sealing subterranean earthformations comprising the use of sodium silicate solutions having acontrolled gel time. More particularly, this invention relates to sodiumsilicate solutions catalyzed by a polyvalent ion which is releasedslowly into the sodium silicate solution.

Various types of materials have been used in oil wells to sealgeological formations therein. Portland cement is one of the more commonsealing agents used in oil wells. Some degree of success has beenachieved using portland cement; however, there are numerous applicationswhere such cement is ineffective. In sealing a formation, a techniqueknown as squeeze cementing is often used. In performing squeezecementing the slurry of portland cement is placed opposite the formationto be sealed and sufficient hydraulic pressure is applied to force theslurry into the formation. As the channels in the formation to be sealedare usually fine capillaries, they are too small to accept cementparticles. The hydraulic pressure applied thus causes the formation tobreak down or fracture. With a split or opening of the formation underpressure, a sheet of portland cement slurry fills the crack formed andthe capillary system of the formation is left essentially intact andunplugged. Other materials such as plasters, pitches, swelling gruels,grain, etc., fail to seal the formation capillaries, in a manner similarto the portland cement. Emulsions are rarely successful because of theirinherent resistance to capillaries caused by the Jamin effect.

The material used as a sealing agent must be a true fluid which iscapable of entry and flow in capillaries, and which upon solidification,plugs or seals the capillaries occupied. The true fluid can be either apure liquid or a solution.

Sodium silicate is a true fluid which is capable of sealing geologicalformations, but has previously been used with little or no success. Someof these prior art methods of sealing or plugging with sodium silicateare disclosed in US. Patents Nos. 2,236,147, 2,198,120 and 2,330,145.

Sodium silicate is a complicated system of various molecular weightsilica polymers'in an alkaline solution. Aside from requiring a certainminimum amount of alkalinity, sodium silicate has no definite chemicalcombining numbers.

Patented Apr. 1, 1969 "ice Sodium silicate may be caused to form a gelwhich will seal an underground formation or plug capillaries by theaddition of polyvalent ions such as Ca++, Fe+++, Cr+++, Cu++, etc.However, the additionof salts such as CaCl,, Fe (SO Cr(NO,) CuSO etc.,will cause essentially immediate gelation which allows no time to pumpthe solution into the formation. Thus, a two-shot system must be usedwherein the sodium silicate and polyvalent ion solutions areindependently pumped into the formation. Such two-shot" systems areundesirable because they require added time and pumping equipment, it isdifficult to obtain proper mixing in the formation, etc. Thus, it isdesired to have a one-shot system wherein all of the ingredients arecontained in a single solution.

It is therefore an object of this present invention to provide acomposition and method for sealing subterranean earth formationsemploying sodium silicate solutions.

It is a further object of the present invention to provide a delayedsetting time for sodium silicate solutions containing polyvalent metalions.

These and other objects of the present invention will be more readilyunderstood from a reading of the follow ing specification and referenceto the examples forming a part thereof.

Summary of the invention Briefly, this invention comprises a sodiumsilicate solution containing a polyvalent ion complex which willdecompose or break down to release the polyvalent ion slowly. In somecases, it may be necessary to include a material which slowly destroysthe complex and thus liberates the polyvalent ion. However, there aresome complexes which slowly release polyvalent ion without the necessityof a complex destroying material. Thus both types of complexes may beused within the scope of the present invention.

Description of the preferred embodiments Any complex that will tie upthe polyvalent ion and. prevent it from causing a setting or gelling ofthe sodium silicate until a complex destroyer is added to liberate thepolyvalent ion may be used in this invention. Illustrative of the comlexes which may be used are K Fe(CN) 4 s .9)3. s)4 4, s T M s)s a) sNaTiCl Zn(NH (N0 )g, Mg(MnO,) etc. A large number of complex ions ofpolyvalent metals exist and are well known to those skilled in the artas illustrated by Moeller, Inorganic Chemistry (1951), pages 227-46,which is hereby incorporated herein by reference.

The compounds listed above are inorganic; the use of organic ligands isnot outside the scope of this invention. Examples of such organic mono,di, tri, and multidentate ligands are: oxalate, ethyl amine, ethylenediamine, diethylene triamine, tetraethylene pentamine, ethylenediaminetetraacetic acid, glycine, dimethyl glyoxine, acetylacetone, thiourea,alpha,alpha-dipyridyl and thiocyanate. In general, the bonding atoms,either singly or as parts of a ligand, are C, N, O, F, Cl, Br, I, P, S,and As. Some di or multivalent ions usable in complexes are: divalentCa, V, Fe, Co, Ni, Cu, Zn, Pd, Pt, Ag, Cd; trivalent C, Al, Sc, Cr, Fe,Co, 0s, Ir, Au; and tetravalent Pt, Pd. It is conceivable that most ofthe metallic elements including the rare earths could be made to servethe part in this invention. However, for economic practicability,precious metals, such as An, Ag, and Pt, and non-com mercial metals areof academic interest mainly.

Solutions of the complexes are incorporated into the sodium silicate tobe used as the chemical grout. A

complex destroyer may also be incorporated into the composition. Thecomplex destroyer must be selected so that it will slowly destroy thecomplex. It destruction of the complex is too rapid, setting of thesodium silicate will occur before it can be introduced into its intendedenvironment. Therefore, the nature and/ or concentration of the complexdestroyer should be such that it liberates the polyvalent ion slowly. Ofcourse, the nature of the complex destroyer will vary with the type ofcomplex selected. Those skilled in the art are familiar with variousmaterials which will complex polyvalent ions and also the materialswhich will destroy these complexes. The ammonia containing complexes,called ammine complexes, have ,been found to be particularly suitable inpracticing this invention.

Complex destroyers are selected from chemicals that will react with thecomplex ligand in such a manner that the ligand can no longerparticipate in the complex. When the ligand is sufiiciently crippled bythe complex destroyer, the naked or partially stripped polyvalent ioncan now be seized by the silicate ion starting gelation of the solution.The chemicals containing carbonyl grou s, algiydes, andketonmimhldehydes arem m ple x ii mfmmand certain ammine complexes.Examples of usable aldehydes would be formaldehyde, acetaldehyde,propionaldehyde, glutaraldehyde, propanediol, hydroxyethanol, and sodium4- benzaldehyde-sulfonate. Keuugs ag lessreactig hutsuch compounds asacetone can prove useful for high temperature applications.

oxidizing agents are good complex destroyers. Strong oxidizing agentssuch as permanganates, chromates, per= oxides, perchlorates and nitratesare applicable but the chromates and permanganates do not performsufficiently well for normal commercial application. The chromates andpermanganates have a side effect of liberating chro mium and manganeseions. Thus the double action of the complex destroyer (itself a complex)and a complex (in this case a complex destroyer also) mutually destroying complexes and liberating multivalent cations is manifested. PWhydrogen peroxide, and the persulfates are particularly useful becausethey function more readily in the alkaline sodium silicate medium.Sodium persulfate will be used later as an example; however, othercations can substitute for sodium such as potassium, ammonium,guanidine, etc.

A particularly suitable complex destroyer which is effective indestroying the complexes set forth above at a rate such thatintroduction of the polyvalent ion into sodium silicate will occurslowly, is formaldehyde. Formaldehyde may be introduced as it is, in acombination with some other material, or as a material which willdecompose in the sodium silicate solution to release the formaldehyde.Examples of formaldehyde sources are a urea formaldehyde such as U.F. 85(a urea formaldehyde resin commercial available from the Allied ChemicalCompany), formalin, paraformaldehyde, etc.

Gel time can be controlled by varying the concentration of the complexand also by varying the concentration of the complex destroyer used. Theconcentration of the complexed polyvalent metal may vary from about 0.02to 1 moi/liter of silicate solution or higher. The complex destroyerconcentration will depend upon its strength and the strength of thecomplex. However, in general, a concentration of about 0.1 to by weightmay be used. For a relatively constant complex concentration, increasingthe ratio of complex destroyer to com plex will decrease the gel time.Thus, the sodium silicate solution containing the polyvalent ion complexand the complex destroyer can be tailored to produce the gel timedesired.

Setting of the silicate may be caused by the liberated polyvalent ion,acidic fragments of the destroyed complex or acidic materials resultingfrom the complex destroyer.

Rather than using a complex which requires a complex destroyer toliberate the polyvalent ion, a complex can be used which slowlyliberates the polyvalent ion without the necessity of having a complexdestroyer present. An example of such a complex is that formed between acarbohydrate and ions of Mg, Zn, Cd, Ca, etc. An effective complex isformed between a calcium salt such as CaO, CaCO CaCl,, etc., anddextrose or sucrose In general, any polyvalent ion-carbohydrate complex.may used. The complex may be destroyed by an oxidizing agent such as NaS O However, the carbohydrate com plex has only moderate stability andthus the presence of a complex destroyer is not necessary.

Other complexing materials which may be used include mannitol, sodiumethylene-diaminetetraacetate, nitrilotriacetic acid, formamide, urea,and ethylacetate may be usedin combination with dextrose or sucrose.

Any suitable sodium silicate may be used in the practice of the presentinvention. An example of a particularly suitable sodium silicatesolution is 41 B sodium silicate solution (e.g., Diamond Alkali Grade 40or Pennsylvania Quartz N brand).

The sodium silicate solution of this invention may be used to sealunderground formations in a manner similar to that disclosed inMcLaughlin et al. application, Ser'. No. 511,141, filed Dec. 2, 1965,and entitled Method of Plugging or Sealing Formations, and now US.Patent No. 3,375,872; the disclosure of which is hereby incorporated byreference. In general, the sodium silicate solution of this inventionmay be used in any application where it is desired to form a delayedsetting gel from a liquid.

The invention can be more fully understood by reference to the followingexamples.

Example I The effect of formaldehyde concentration and complexconcentration on gel time and relative gel strength was explored. Thesodium silicate used was 40 Grade sodium silicate. The copper complexwas made by mixing 180 gms. of CuSOySI-hO, 450 ml. H 0, 420 ml. 28%Nl-LOH solution and enough water to make 1000 ml. of thetetramminecopper (II) sulfate solution. The formaldehyde was added as a37% solution of formaldehyde. To the silicate, copper complex andformaldehyde mixture, enough water was added to make ml. final volume.The test temperature was 75 F. The gel time and relative strength of thegel was measured. The results are set forth in Table I. The gel having astrength of 1 was the strongest and compared with parafi'ln. The 10 gelwas mushy but was strong enough to suspend a stirring rod.

TABLE I 37% Formal- Copper Gel Time, Relative Run No. dehyde, ml.Solution, ml. min.

Strength The 37% formaldehyde solution used in this and subsequenttables is 37% by weight formaldehyde in a water-methanol solvent. Thismix is commonly called formalin.

* 1 minute 10 seconds. l Overnight.

Example 11 available from the Allied Chemical Company. The test wasperformed using the method set forth in Example I. The gels formed withthe copper and the nickel com- The results are given in Table II. plexwere excellent. The cobalt, chromium and cadmium TABLE II Bun CopperAmount, Gel Time. Gel No. 8023MB, Chemicals ml. minutes Strength 1 Color0! Gel i "'33 Trlnnethyloinltromethane L 36 1 Dark. 33 .....do' l5 36 1Medium. 25 .F. e 4 Light.

g y l Aoetaeh $34 5 2 Very light 0111181 e el 115%, NM 0:. 18 l 4 5 eaU. as e 4 a anal-k.

17.? 85. Q 12 8 -Very dark. v.1 4 2a a :Medlum am. U1 3 13% 4 Very dark.I as or ,s a ildedium. as I] F 4 a Dark.

l This is a relative gel strength, a 1 rating is a hard brittlewax and a6 rating is a little harder than custard.

'ihe darkiiess or lightness of the blue color is e muglnindlcator of theamount of Tetrammlneeopper (II) sulfate When all 0! the Tetrammlneco peris gone, a very light blue remains.

l (HOCHQQCNOr-e 61.5 EIIL/HD ml. solution water, pH adjusted to 8 withNaOH,

4 Same as above but pH adjusted to ll with NeOH.

Tris (methylol) nitromethane decomposes to formal- 20 containingsolutions resulted in a precipitate which was dehyde and nitromethane inalkaline solutions. However, P y f y q of tha metal- The precipitate inthe rapid ge l time of only one-half minute was apparently thc cadmmmwas not heavy and would not W caused by the acidity of the nitromethaneproduced. vent use of thls'matenal' In run four, ethyl acetate was usedin conjunction with Example IV formaldehyde. Hydrolysis of ethyl acetateto make ethyl The propeifics of a g 61 formed according to the Proalcohol and to Set ff may be cedure of Example III for copper and nickelwere deterused alone as a method of setting sodium silicate (see minedin this cxampla The f ld h d source was Patent In full fi S d l i eeither U.F. 85 or 37% aqueous formaldehyde solution.

was used with the formaldehyde. There was a rapid set The results areset forth in Table IV.

TABLE IV Formaldehyde Amount Formaldehyde Gel Time, CuSO -5H,O Gel Time,NiSO.-6H O Bun No. Complex, ml. Complex Retlo minutes Penetrometerminutes Penetrometer Source Amount, ml. Reading Reading 3:2,. 7 as 0.1209 11s 13 92 a7 10 2s 0 160 4 41 a 29 3 rm 25 0 200 2 45 1 as U .F. 4 250 12a 27 100 57 85 U1. 7 2s 0 21s 8 5s 18 45 U .1. 10 25 o. 312 4 5 47 740 as 2 l8 3% a a e UIF'. 1 30 6.1252 4 as 14 a1 U.F.s5 7 0.156 4 a1 132s Grams formaldehyde/ml. complex. but the sodium aluminate did notappear to greatly in- 01 Example V fi "8* This exarilple illustrates theuse of various carbohy Example III drate completing agents. Many ofthese agents will liber- Several metal complexes were prepared using thefolate the polyvalem Slowly and thus. do not require the lowing pr hue.An amine complex was formed by use of a complex destroyer. Two solutionswere prepared, mixing 180 gms. of metal salt, 450 ml. of water, 420 ml.the first bemg a .soluuon f the polyvalem 9 W 16X and the second being asolution of 40 grade S0dllllIl silicate.

of 28% NI-l Ol-I solution and enough water to "make 1000 5 ml. ofsolution. The sodium silicate grouting solution was 'Nazszoa was as a i'some then prepared by mixing two solutions. The first solution g and sthe sodmm sflicate solunon contained 33 ml. of 40 grade sodium silicate,a variable 2322 z gf fi g s i g gg a z gz f zs l amount of forma dehydesolution, and enough water to together and m another method the complexoomammg ma 6 ml of the first solution The second somnon solution was inected into the sodium silicate containing contained a variable amount ofthe complex solution prepared as indicated above and enough water tomake 50 sohmon with a syrmge The mlectlon method appeared ml. The twosolutions were then added to make the grout- 5 Produce better resultsIhe I are Se} forth below in Table V. The presence of initial nonuniformgelling,

mg solution The results are set forth m Table flockballs, may beundesirable and was noted in this experiment.

Data

TABLE m The data are presented in the following table:

Complex U.F.85 in Gel Solution Solution A, Time Remarks Code:

AJB-Solution A injected into Solution B with a a s Excellen syringe. gAPB-Solution A poured into Solution B. a 10min.. Intezg igecipltatg i wBPA-Solution B poured into Solution A.

m X-A solution of 0.2 gm./ml. Na sp added. H el 8 mesa slifi fi Z-Asolution of 0.1 gm./m.l. Na,s,o chromumnu 5 m lf, gait 40SS -Dia mondAlkali 40 Grade odtum S1l1cate Cadium a m Somewhat s imllarto cobalt (41Be, Na- O:S1O =l :322)

gf ggg g ggg g CaCit-Caleium Citrate. precipitate. SEDTA-SodiumEthylenediaminetetraaoetate.

Sl'P-Sodium Tripolyphosphate.

7 8 NTA-Nitrilotriacetic Acid. 3. The composition of claim 1 wherein thecomplex is CaLCalcium Lactate. an ammine complex. CaA/C Afieiaifi 4. Thecomposition of claim 3 wherein the complex FAFormamide.

is a copper-ammine complex. ETAc-Ethyl Acetate.

5. The composition of claim 3 wherein the complex All tests and allsolutions were at 72 F. 5 is a nickel-ammine complex.

TABLE V Mixing Run No. Component Solution A Composition Solution B GelTime Gel Mode Flock-Bailing 1 2.8 gm. :10, 13 gm. Sucrose, 17 m1. H,0,10gm. Nmsmt, APB Moderate 1 min Hard.

50ml. mo. 331:1].4085. 2 2.8 015% 13 gm. Sucrose, 17 ml. 11,0, 33 n11.40SS APB Slight to Moderate... 10 mm Do.

50 a 3 2.8 gm. 05 0,15 gm. Mannitol... 17ml. H1O, 33ml. 40 SS APBModerate 12 min. Do. 2.8 gm. CaO, 15 gm. Mannitol..- 17 m1. 11,0, 33 ml.40 SS... AJB Slight to Moderate Do. 2.8 ggj e o 15 gm. Sucrose, 50 ml.3,0, 50 ml. 40 ss.----.. Pf..- .-.-do.. Do.

35 1 6 2 ClaOH, 18 gm. Sucrose, 601.111.1110, bgm. Na,S,0L APB..-Blight. 71 min... Medium hardv 1 m 7 (iiflimgm. Dextrose,50ml.H,O,50ml.40SS.- AIB.... Moderate 30min. s. 10 gm. Dextrose, 50ml.11,0-.-" 50ml.X,50m1.40SS BPA None 34 hours.... Medium- 9. 10grghDfixgose, 1 gm. CaO, 50ml. X, 50:211. 40 SS BPA Moderate 30minn...Medium hard.

50 10 io c g, 10 gm. Dextrose, 50ml. X, 50ml. 40 BS BPA 5min........Hard.

. 1 11 10gn;1Dfixg0se,1gm. C80, 60ml.Z,50ml.40SS AJB Slight 24m1n Mediumhard 50 12 10 ZHI1l1DfiX gOS8,2 gm. 0801,, 60ml. 2, 5011:1110 ss. AJBVery heavy 50 a 13 10 %1n. Dxezxgogefi4 gm. CaCli, 50ml. Z, 150ml. 40 SSAJB Instant He d. 14 15 gmImStkcrgse, 1.5 gm. CeO, 50ml. X, 60:11140$8.-.. AJB Moderate 7m.in D0.

50 1 15 15 gm. Dextrose, 1.5 gm. CeO, 50ml. X, 60 ml. 40 SS AJBn do 2min Do. 16 15%11fic 185 6, 1 gm. 080, 5011112, 50ml. 40 SS AJB None23min Medium. 11 20 gm. supra, 10 gm. Sucrose, 50 ml. x, 50 ml. .0 ssBPA .....do

2 gm. CaO, 30 gm. H10. 18 15 gm. Dextrose, 1.5 gm. CaO, 50m1.X, 60m1.40SS EPA...

50 ml. H 0. 19.. 10 gm. N'IA, 10 gm. STP, 2 D0.

gm. CB H5 20.. 10 gm. S'IP, 10 gm. Sucrose, 60 m1. X, 50 ml. 40 SS BPAdo 3 hrs Medium hard.

2gm. C80, 50ml. 13,0. 21. 3gm. CeL, 60ml. H1O 50ml. H O, 501ml. 40 SSBPA Moderate 3 hrs Very soft. 22. 2gm. C8Ac,50ml.HgO 50ml. 11,0,501111.40 SS BPA ..do 96min It. 23 10 gm. SEDTA, 10 gm. Dex- 50ml. Z, 60 ml. 40SS BPA.. None 1 min. Medium hard.

trose, 2 gm. C80, 50 ml. H 0. 1 24 1015116 FA,2gm. 080,50ml. 50ml.H,O,b0ml.4OBS....... BPA None 58mm Herd.

I 2b 105%n11]3lEITi.%)c, 2 gm. C80, 50 H11. H10, 60ml. 40 SS BI-LL .do30 min., Very hard.

1 j 25 fifilstficrgse, 1gm.CeO, 50 ml. X, 60 ml. 40 SS BPA Very heavy 18min Hard.

- I 27 lfirgfiSgcrgse, 1.5 gm. CeO, 50ml.X,50m.l.40SS BPA ..do 8min D0.

. g 2S w Dleixgose, 1.0 gm. CaO, 50ml. X, 50ml. 40 SS BPA do 13 min Do.

I j 29 lfigrgilDfixlgose, 1.5 gm. C80, 50ml. X, 50 ml. 40 SS BPA Veryheavy (paste) 7 min... Medium herd.

. I 30 15 %nx1 D e xgose, 1.0 gm. CeO, 50m1.H10, 50ml. 88-..... EPAMedium 104 min a1 155%m. btose, 1.5 gm. CaO, som1.H,0,5om1.40 ss I 32 15%m StI1icr8se, 1.0 gm. CeO, ml. 11 0, 501211.40 SS BPA j 33 15 %11 1 Sl1 cr8se, 1.5 gm. CaO, 50 mi. 1110, ml. 40 SS AJB Blight 17 min I 34 wgli Dgxtose, 1.0 gm. CsO, 50ml. X, 50ml. 40 SS AJB Medium 9min Hard.

- i 35. 15 gm. Dextrose, 0.75 gm. OaO, 50ml. X, 150ml. 40 SS AJB None 39min....... Do.

50 ml. H10.

1 Could not be determined.

The above examples are merely intended as illustrative 6. Thecomposition of claim 3 wherein a formaldehyde of the invention and arenot intended to be limiting. Thus, is present as a complex destroyer. itcan be seen by those skilled in the art that many varia- 60 7. Thecomposition of claim 3 wherein an aldehyde is tions, both as tocomposition and method of mixing and present as a complex destroyer.incorporating the silicate solution can be made without 8. Thecomposition of claim 1 wherein the complex departing from the scope ofthis invention. Furthermore, is a polyvalent ion complexed with acomplexing agent it can be seen that various complex and combinations ofselected from the group consisting of sucrose, dextrose, complexes canbe used with polyvalent ions. Furthermore, mannitol, sodiumethylcnediaminetetraacetate, nitrilothe complexes may be used with orwithout a complex triacetic acid, formamide, urea, and ethylacetate andmixdestroyer to slowly liberate polyvalent ions and the detures thereof.

sired gel time. Therefore, the invention should be limited 9. Thecomposition of claim 8 wherein the complex only by the lawful scope ofthe appended claims. is a calcium-sucrose complex.

We claim: 10. The composition of claim 8 wherein the complex 1. Asealing composition comprising a sodium silicate, is acalcium-dcxtrosccomplex. a polyvalent metal complex and a chemical complex 11. Thecomposition of claim 8 wherein an oxidizing destroyed which reacts withsaid complex whereby the agcntisprcsent asacomplex destroyer. polyvalention in said complex is slowly liberated. 12. A method of plugging orsealing earth formations 2. The composition of claim 1 wherein thematerial and the like, comprising the step of introducing into thecapable of destroying the complex is an oxidizing agent. earth formationto be sealed, a sodium silicate solution,

a polyvalent metal complex and a chemical complex destroyer which reactswith said complex whereby the polyvalent metal ion in said complex isslowly liberated to thereby cause setting of the sodium silicatesolution.

13. The method of claim 12 wherein the material capable of destroyingthe polyvalent meal is an oxidizing agent.

14. The method of claim 12 wherein the complex is an ammine complex.

15. The method of claim 14 wherein the complex is a copper-amminecomplex.

16. The method of claim 14 wherein the complex is a nickel-amminecomplex.

17. The method of claim 14 wherein formaldehyde is added as a complexdestroyer.

18. The method of claim 14 wherein an aldehyde is added as a complexdestroyer.

19. The method of claim 12 wherein the complex is a polyvalent ioncomplexed with a complexing agent selected from the group consisting ofsucrose, dextrose, mannitol, sodium ethylenediaminetetraacetate,nitrilotriacetic acid, formamide, urea, and ethylacetate and mixturesthereof.

20. The method of claim 19 wherein the complex is a calcium-sucrosecomplex.

21. The method of claim 19 wherein the complex is a calcium-dextrosecomplex 22. The method of claim 19 wherein an oxidizing agent is presentas a complex destroyer.

References Cited UNITED STATES PATENTS 2,208,766 7/1940 Lawton 166-292,302,913 11/1942 Reimers 16629 X 2,827,384 3/1958 Freyhold 106-742,968,572 1/1961 Peeler 106-74 3,202,214 8/1965 McLaughlin l6629 X3,294,563 12/1966 Williams 106-74 STEPHEN J. NOVOSAD, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,435,899 April 1, 1969 Homer C. McLaughlin et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, line 46, cancel "(Cr(NH NO )C1 and insert the same at the endof line 45, same column 2. Column 3, line 25, "ammine" should read amineColumns 5 and 6, TABLE IV, third column, line 1 thereof, "7" should read7 1/2 Columns 7 and 8, TABLE V, sub-heading to the fifth column,"Flock-Balling" should read Flockballing Column 7, line 73, "destroyed"should read destroyer Column 9, line 6, "meal" should read metal Signedand sealed this 14th day of April 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

